<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
<script>
    var n = parseInt(prompt("请输入一个数字n，计算1*2*3*···*n"));
    var result = 1;
    for(var i = 1;i<= n;i++){
        result*=i;
    }
    alert("阶乘结果是" + result)
</script>
</html>